1. Field of the Invention
This invention relates in general to certain new and useful improvements in digitizing scanning apparatus and to drive systems for digitizing scanning apparatus and, more particularly, to a drive system which enables a constant drive pressure against a document being scanned regardless of document thickness and which also eliminates any chatter or vibration which could otherwise result in interference with the scanning and reading operation.
2. Brief Description of the Related Art
In recent years, there has been a increased interest in digital scanning apparatus for purposes of generating a digital image of a document which may be transmitted via telephone links or the like. One area in particular which finds effective use of a digitized image of a document is the medical industry in which digital images of x-rays, mammograms and the like can be made for record and storage purposes and which can also be transmitted to a remote site for reading by an expert in a particular area of radiological reading and scanning.
One of the principle problems which occur with the conventionally available drive systems is that the drive system must be capable of accommodating films or other documents of varying thicknesses. Thus, one document may have a slightly different thickness compared to another document. Even more so, there are even non-linearities in the thicknesses of a document, such as a light transmissive film. Unless the drive system is capable of accommodating these non-linearities, different drive pressures will result and, hence, the documents may be driven at different speeds and even at varying speeds. This, in and of itself, will materially interfere with the accuracy of material which is scanned and, hence, the accuracy of any document which is read.
In the prior art drive systems, all of the drive rollers which were used for moving of the film or other document were not necessarily driven at the same surface speed. This difference in surface velocity, no matter how small, resulted in chatter in the film or other document. In addition, either the drive rollers or the idler rollers, or both, were formed of a material which provided a reasonable coefficient of friction, such as rubber or the like. Although this provided good contact, the amount of force applied by the roller would vary from roller to roller. This coupled with variations in film thickness affected the force applied to the film and, hence, the accuracy of driving of the film through the system.
In one prior art digitizing scanning apparatus, a document was moved through a scanning path by means of a drive mechanism which relied upon drive rollers and cooperating idler rollers. However, the idler rollers and the drive rollers were fixed in position relative to one another in order to create a gap approximately the thickness of the document being fed. This device provided no adjustability and, therefore, a document of non-uniform thickness or otherwise a document having a greater or lesser thickness than normal resulted in different driving pressure on that document. Hence, there was a variation in the speed of the document passing through the scanning path.
One prior art device which was moderately effective was that taught in my U.S. Pat. No. 5,093,734, dated Mar. 3, 1992. In this digitizing drive system, a plurality of floating idler rollers were used with drive rollers disposed beneath the idler rollers. The idler rollers were mounted for vertical shiftable movement in order accommodate documents having a greater or lesser thickness then the gap between the rollers. Adjustment screws were even provided for this purpose. However, the adjustability did not overcome the precise need for uniform driving pressure imposed on the document and clearly did not overcome the chatter resulting from the drive system.
There has been a need for a drive system capable of moving documents through a scanning path with uniform pressure applied to the document regardless of document thickness and also which does not create any chatter in the driving process.
It is, therefore, one of the primary objects of the present invention to provide a drive system for digitizing scanning apparatus which allows for a document to be driven through a scanning path with a uniform drive pressure and at a uniform speed regardless of variations in the thickness of the document or variations between thicknesses of successive documents.
It is another object of the present invention to provide a drive system for digitizing scanning apparatus of the type stated in which both drive rollers and idler rollers are mounted in such manner that chatter or other vibration does not result with respect to the document being scanned.
It is a further object of the present invention to provide a drive system for digitizing scanning apparatus of the type stated in which idler rollers and drive rollers are mounted in such manner that they automatically separate to provide a gap of proper thickness for a document being driven without requiring manual intervention and which nevertheless provides a uniform driving pressure.
It is an additional object of the present invention to provide a drive system for digitizing scanning apparatus of the type stated which can be constructed at a relatively low cost, but which is nevertheless highly efficient in operation.
It is still another object of the present invention to provide a drive system for digitizing scanning apparatus of the type stated which provides indication if the document being scanned is not moving or is otherwise not moving at a proper speed.
It is another salient object of the present invention to provide a method for moving a document through a scanning apparatus with generally uniform driving force applied to the document independently of the thickness of the document and which eliminates any potential imposition of chatter on that document.
With the above and other objects in view, my invention resides in the novel features of form, construction, arrangement and combination of parts presently described and pointed out in the claims.
The present invention relates primarily to a drive system used with digitizing scanning apparatus. The digitizing scanning apparatus of the type with which the drive system is used generally scans a document, such as a light transmissive document in the nature of an x-ray or a mammogram or the like, and stores a digital signal representative of that document. The stored digital signals in combination can be transmitted as, for example, over telephone lines or the like, and regenerated to create a copy of that image at a distant location.
The drive system of the present invention is designed to move a document being scanned through the scanning apparatus in such manner that it will always move at a uniform drive speed regardless of differences in the thickness between successive documents or regardless of variations in the uniformity of thickness of a document. The drive system is uniquely constructed to automatically accommodate for these thickness variations. In addition, the drive system is constructed so that no chatter or vibration is imposed on the document being driven, such that uniform and accurate scanning can be obtained.
The drive system of the invention includes three main drive rollers which are loaded against one another, although they do have some floating characteristics. The loading is vertically arranged, such that an uppermost roller applies pressure to an intermediate roller which, in turn, applies a driving pressure to a lowermost of the rollers. A pair of idler rollers are also employed and are arranged to be in contact with or otherwise juxtaposed to the uppermost of the drive rollers and the lowermost of the drive rollers. No springs are employed in the mounting of the rollers, and hence, there is no variation in force provided by springs.
The idler rollers are actually mounted in a floating manner on pins so that the idler rollers can be shifted slightly away from the drive rollers in order to accommodate film thickness variations. The idler rollers are effectively floated for a limited degree so that each idler roller can be biased upwardly or downwardly and to a slight degree away from or toward the drive roller against which it is juxtaposed. This occurs automatically without the need for adjustment screws, such as set screws.
The invention can be described in general terms as a drive system for a digitizing scanning apparatus and which provides for scanning and digitizing information on a document. The drive system allows for a uniform driving force to be applied to a scanned document without the imposition of a chatter to that document. In this case, the drive system comprises a first drive roller and a second drive roller located in generally vertically spaced apart arrangement. A third drive roller is located intermediately between and has its axis of rotation offset from the axis of rotation of the first and second drive rollers. The third drive roller provides a driving contact between the first two drive rollers.
Means provides a driving force to one of the drive rollers causing this drive roller to become a powered drive roller. This driving force is imparted to the other of the drive rollers. Finally, at least one idler roller is disposed in juxtaposed relationship to one of the drive rollers and remains in contact with that drive roller until a document is received. The idler roller then shifts in response to thickness of the document and forms a gap between the drive roller of proper thickness to receive the document therebetween. That gap is only the thickness of the document.
In more detail, the idler roller is a floating idler roller, such that it can be biased upwardly and away from the drive roller with which it cooperates. In a more preferred embodiment, a pair of the idler rollers are employed. In this preferred arrangement, one of the idler rollers operates in juxtaposed relationship to a first of the drive rollers and a second of the idler rollers operates in juxtaposed relationship to the second of the drive rollers. The idler rollers and the associated drive rollers are located so that the idler rollers shift and form a gap of proper thickness to which receive the document to be scanned. Thus, the idler roller and associated driver roller are always in contact and ready to receive a document to be scanned.
The invention possesses many other advantages and has other purposes which may be made more clearly apparent from a consideration of the forms in which it may be embodied. These forms are shown in the drawings forming a part of and accompanying the present specification. They will now be described in detail for purposes of illustrating the general principles of the invention, but it is to be understood that such detailed description is not to be taken in a limiting sense.